渤海油田油井酸化返排液固悬物含量分析

Analysis of the Content of Solid Suspended Matter in Acid Fracturing Flowback Fluids from Oil Wells in Bohai Oilfield

针对渤海油田油井酸化返排液简易处理后回注造成的回注井堵塞问题,分析了渤海油田现场三口油井酸化返排液的固悬物含量,并通过改变酸碱环境,进一步分析了酸碱环境对酸化返排液中固悬物含量的影响。实验表明,不同单井、单井不同返排周期返排液中固悬物含量差异明显,酸碱环境对固悬物含量影响很大,加碱中和后的酸化返排液中会产生大量的Fe(OH)_(3)沉淀。室内填砂管动态驱替实验表明,去浮油后的pH值为1~2的酸化返排液,不会对填砂管造成明显堵塞。现场施工过程中,酸化返排液应避免加碱中和,同时使用盐酸体系降低返排液pH值,可有效减少返排液中固悬物含量,降低回注井近井堵塞风险。

Acid fracturing flowback fluids produced in Bohai oilfield,after simple treatment,were reinjected into the formation.The fracturing flowback fluids always caused the injectors to be blocked because of the existence of solid suspended matter in the fracturing flowback fluids.Laboratory experiments were conducted for the suspended solid matter on three fracturing flowback fluid samples taken from oil wells in Bohai oilfield.The effect of pH on the content of suspended solid matter in the acid fracturing flowback fluids was analyzed by changing the pH value of the fracturing fluids.The experimental results showed that the content of the suspended solid matter in fracturing flowback fluids from different wells and the content of suspended solid matter in the fracturing flowback fluid from a single well in different time of flowback are quite different.pH value plays an important role in the content of the suspended solid matter.Large amount of Fe(OH)_(3) precipitate is produced in acid fracturing fluid neutralized with bases.Dynamic displacing test through sandpack tube showed that de-oiled acid fracturing flowback fluid with pH 1–2 does not cause obvious block in the sandpack tube.It is thus understood that in field operation,the acid fracturing flowback fluid should not be neutralized with bases.If HCl is used to reduce the pH value of the fracturing flowback fluid,the content of the suspended solid matter in the fracturing fluid can be effectively decreased,hence reducing the risk of near-wellbore blocking in injectors.